The effect of other organisms on the survival rate of Aphodius tasmaniae Hope (Scarabaeidae) in the lower south east of South Australia.

Abstract

The survival rate of the univoltine species Aphodius tasmaniae in improved pastures in the lower south-east of South Australia is influenced by individuals of the same species (i.e. by density) and by individuals of many other species. The species is distributed patchily with areas of high density interspersed with more extensive areas of low density. In the areas of high density, competition for food occurs and larvae may "fight". Such fights result in deaths, but there is little evidence of high mortality resulting from competition and little evidence that "density-induced combat" governs the number of the species. Of the other species which influence A. tasmaniae it is considered that the entomophagous fungus Cordyceps aphodii Mathieson is the only one which, in conjunction with water in winter, causes a sufficiently variable mortality from year to year to contribute significantly towards changes in numbers of A. tasmaniae from generation to generation.